TCP/IP - Laser Range Finder Bricklet

This is the description of the TCP/IP protocol for the Laser Range Finder Bricklet. General information and technical specifications for the Laser Range Finder Bricklet are summarized in its hardware description.

API

A general description of the TCP/IP protocol structure can be found here.

Basic Functions

BrickletLaserRangeFinder.get_distance
Function ID:

1

Request:

empty payload

Response:
  • distance -- uint16

Returns the measured distance. The value has a range of 0 to 4000 and is given in cm.

Sensor hardware version 1 (see get_sensor_hardware_version) cannot measure distance and velocity at the same time. Therefore, the distance mode has to be enabled using set_mode. Sensor hardware version 3 can measure distance and velocity at the same time. Also the laser has to be enabled, see enable_laser.

If you want to get the distance periodically, it is recommended to use the CALLBACK_DISTANCE callback and set the period with set_distance_callback_period.

BrickletLaserRangeFinder.get_velocity
Function ID:

2

Request:

empty payload

Response:
  • velocity -- int16

Returns the measured velocity. The value has a range of -12800 to 12700 and is given in 1/100 m/s.

Sensor hardware version 1 (see get_sensor_hardware_version) cannot measure distance and velocity at the same time. Therefore, the velocity mode has to be enabled using set_mode. Sensor hardware version 3 can measure distance and velocity at the same time, but the velocity measurement only produces stables results if a fixed measurement rate (see set_configuration) is configured. Also the laser has to be enabled, see enable_laser.

If you want to get the velocity periodically, it is recommended to use the CALLBACK_VELOCITY callback and set the period with set_velocity_callback_period.

BrickletLaserRangeFinder.set_mode
Function ID:

15

Request:
  • mode -- uint8
Response:

no response

Note

This function is only available if you have a LIDAR-Lite sensor with hardware version 1. Use set_configuration for hardware version 3. You can check the sensor hardware version using get_sensor_hardware_version.

The LIDAR-Lite sensor (hardware version 1) has five different modes. One mode is for distance measurements and four modes are for velocity measurements with different ranges.

The following modes are available:

  • 0: Distance is measured with resolution 1.0 cm and range 0-400 cm
  • 1: Velocity is measured with resolution 0.1 m/s and range is 0-12.7 m/s
  • 2: Velocity is measured with resolution 0.25 m/s and range is 0-31.75 m/s
  • 3: Velocity is measured with resolution 0.5 m/s and range is 0-63.5 m/s
  • 4: Velocity is measured with resolution 1.0 m/s and range is 0-127 m/s

The default mode is 0 (distance is measured).

The following meanings are defined for the parameters of this function:

  • 0: distance, for mode
  • 1: velocity max 13ms, for mode
  • 2: velocity max 32ms, for mode
  • 3: velocity max 64ms, for mode
  • 4: velocity max 127ms, for mode
BrickletLaserRangeFinder.get_mode
Function ID:

16

Request:

empty payload

Response:
  • mode -- uint8

Returns the mode as set by set_mode.

The following meanings are defined for the parameters of this function:

  • 0: distance, for mode
  • 1: velocity max 13ms, for mode
  • 2: velocity max 32ms, for mode
  • 3: velocity max 64ms, for mode
  • 4: velocity max 127ms, for mode
BrickletLaserRangeFinder.enable_laser
Function ID:17
Request:empty payload
Response:no response

Activates the laser of the LIDAR.

We recommend that you wait 250ms after enabling the laser before the first call of get_distance to ensure stable measurements.

BrickletLaserRangeFinder.disable_laser
Function ID:18
Request:empty payload
Response:no response

Deactivates the laser of the LIDAR.

BrickletLaserRangeFinder.is_laser_enabled
Function ID:

19

Request:

empty payload

Response:
  • laser_enabled -- bool

Returns true if the laser is enabled, false otherwise.

BrickletLaserRangeFinder.set_configuration
Function ID:

25

Request:
  • acquisition_count -- uint8
  • enable_quick_termination -- bool
  • threshold_value -- uint8
  • measurement_frequency -- uint16
Response:

no response

Note

This function is only available if you have a LIDAR-Lite sensor with hardware version 3. Use set_mode for hardware version 1. You can check the sensor hardware version using get_sensor_hardware_version.

The Aquisition Count defines the number of times the Laser Range Finder Bricklet will integrate acquisitions to find a correlation record peak. With a higher count, the Bricklet can measure longer distances. With a lower count, the rate increases. The allowed values are 1-255.

If you set Enable Quick Termination to true, the distance measurement will be terminated early if a high peak was already detected. This means that a higher measurement rate can be achieved and long distances can be measured at the same time. However, the chance of false-positive distance measurements increases.

Normally the distance is calculated with a detection algorithm that uses peak value, signal strength and noise. You can however also define a fixed Threshold Value. Set this to a low value if you want to measure the distance to something that has very little reflection (e.g. glass) and set it to a high value if you want to measure the distance to something with a very high reflection (e.g. mirror). Set this to 0 to use the default algorithm. The other allowed values are 1-255.

Set the Measurement Frequency in Hz to force a fixed measurement rate. If set to 0, the Laser Range Finder Bricklet will use the optimal frequency according to the other configurations and the actual measured distance. Since the rate is not fixed in this case, the velocity measurement is not stable. For a stable velocity measurement you should set a fixed measurement frequency. The lower the frequency, the higher is the resolution of the calculated velocity. The allowed values are 10Hz-500Hz (and 0 to turn the fixed frequency off).

The default values for Acquisition Count, Enable Quick Termination, Threshold Value and Measurement Frequency are 128, false, 0 and 0.

New in version 2.0.3 (Plugin).

BrickletLaserRangeFinder.get_configuration
Function ID:

26

Request:

empty payload

Response:
  • acquisition_count -- uint8
  • enable_quick_termination -- bool
  • threshold_value -- uint8
  • measurement_frequency -- uint16

Returns the configuration as set by set_configuration.

New in version 2.0.3 (Plugin).

Advanced Functions

BrickletLaserRangeFinder.set_moving_average
Function ID:

13

Request:
  • distance_average_length -- uint8
  • velocity_average_length -- uint8
Response:

no response

Sets the length of a moving averaging for the distance and velocity.

Setting the length to 0 will turn the averaging completely off. With less averaging, there is more noise on the data.

The range for the averaging is 0-30.

The default value is 10.

BrickletLaserRangeFinder.get_moving_average
Function ID:

14

Request:

empty payload

Response:
  • distance_average_length -- uint8
  • velocity_average_length -- uint8

Returns the length moving average as set by set_moving_average.

BrickletLaserRangeFinder.get_sensor_hardware_version
Function ID:

24

Request:

empty payload

Response:
  • version -- uint8

Returns the LIDAR-Lite hardware version.

The following meanings are defined for the parameters of this function:

  • 1: 1, for version
  • 3: 3, for version

New in version 2.0.3 (Plugin).

BrickletLaserRangeFinder.get_identity
Function ID:

255

Request:

empty payload

Response:
  • uid -- char[8]
  • connected_uid -- char[8]
  • position -- char
  • hardware_version -- uint8[3]
  • firmware_version -- uint8[3]
  • device_identifier -- uint16

Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.

The position can be 'a', 'b', 'c' or 'd'.

The device identifier numbers can be found here

Callback Configuration Functions

BrickletLaserRangeFinder.set_distance_callback_period
Function ID:

3

Request:
  • period -- uint32
Response:

no response

Sets the period in ms with which the CALLBACK_DISTANCE callback is triggered periodically. A value of 0 turns the callback off.

The CALLBACK_DISTANCE callback is only triggered if the distance value has changed since the last triggering.

The default value is 0.

BrickletLaserRangeFinder.get_distance_callback_period
Function ID:

4

Request:

empty payload

Response:
  • period -- uint32

Returns the period as set by set_distance_callback_period.

BrickletLaserRangeFinder.set_velocity_callback_period
Function ID:

5

Request:
  • period -- uint32
Response:

no response

Sets the period in ms with which the CALLBACK_VELOCITY callback is triggered periodically. A value of 0 turns the callback off.

The CALLBACK_VELOCITY callback is only triggered if the velocity value has changed since the last triggering.

The default value is 0.

BrickletLaserRangeFinder.get_velocity_callback_period
Function ID:

6

Request:

empty payload

Response:
  • period -- uint32

Returns the period as set by set_velocity_callback_period.

BrickletLaserRangeFinder.set_distance_callback_threshold
Function ID:

7

Request:
  • option -- char
  • min -- uint16
  • max -- uint16
Response:

no response

Sets the thresholds for the CALLBACK_DISTANCE_REACHED callback.

The following options are possible:

Option Description
'x' Callback is turned off
'o' Callback is triggered when the distance value is outside the min and max values
'i' Callback is triggered when the distance value is inside the min and max values
'<' Callback is triggered when the distance value is smaller than the min value (max is ignored)
'>' Callback is triggered when the distance value is greater than the min value (max is ignored)

The default value is ('x', 0, 0).

The following meanings are defined for the parameters of this function:

  • x: off, for option
  • o: outside, for option
  • i: inside, for option
  • <: smaller, for option
  • >: greater, for option
BrickletLaserRangeFinder.get_distance_callback_threshold
Function ID:

8

Request:

empty payload

Response:
  • option -- char
  • min -- uint16
  • max -- uint16

Returns the threshold as set by set_distance_callback_threshold.

The following meanings are defined for the parameters of this function:

  • x: off, for option
  • o: outside, for option
  • i: inside, for option
  • <: smaller, for option
  • >: greater, for option
BrickletLaserRangeFinder.set_velocity_callback_threshold
Function ID:

9

Request:
  • option -- char
  • min -- int16
  • max -- int16
Response:

no response

Sets the thresholds for the CALLBACK_VELOCITY_REACHED callback.

The following options are possible:

Option Description
'x' Callback is turned off
'o' Callback is triggered when the velocity is outside the min and max values
'i' Callback is triggered when the velocity is inside the min and max values
'<' Callback is triggered when the velocity is smaller than the min value (max is ignored)
'>' Callback is triggered when the velocity is greater than the min value (max is ignored)

The default value is ('x', 0, 0).

The following meanings are defined for the parameters of this function:

  • x: off, for option
  • o: outside, for option
  • i: inside, for option
  • <: smaller, for option
  • >: greater, for option
BrickletLaserRangeFinder.get_velocity_callback_threshold
Function ID:

10

Request:

empty payload

Response:
  • option -- char
  • min -- int16
  • max -- int16

Returns the threshold as set by set_velocity_callback_threshold.

The following meanings are defined for the parameters of this function:

  • x: off, for option
  • o: outside, for option
  • i: inside, for option
  • <: smaller, for option
  • >: greater, for option
BrickletLaserRangeFinder.set_debounce_period
Function ID:

11

Request:
  • debounce -- uint32
Response:

no response

Sets the period in ms with which the threshold callbacks

are triggered, if the thresholds

keep being reached.

The default value is 100.

BrickletLaserRangeFinder.get_debounce_period
Function ID:

12

Request:

empty payload

Response:
  • debounce -- uint32

Returns the debounce period as set by set_debounce_period.

Callbacks

BrickletLaserRangeFinder.CALLBACK_DISTANCE
Function ID:

20

Response:
  • distance -- uint16

This callback is triggered periodically with the period that is set by set_distance_callback_period. The response value is the distance value of the sensor.

The CALLBACK_DISTANCE callback is only triggered if the distance value has changed since the last triggering.

BrickletLaserRangeFinder.CALLBACK_VELOCITY
Function ID:

21

Response:
  • velocity -- int16

This callback is triggered periodically with the period that is set by set_velocity_callback_period. The response value is the velocity value of the sensor.

The CALLBACK_VELOCITY callback is only triggered if the velocity has changed since the last triggering.

BrickletLaserRangeFinder.CALLBACK_DISTANCE_REACHED
Function ID:

22

Response:
  • distance -- uint16

This callback is triggered when the threshold as set by set_distance_callback_threshold is reached. The response value is the distance value of the sensor.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by set_debounce_period.

BrickletLaserRangeFinder.CALLBACK_VELOCITY_REACHED
Function ID:

23

Response:
  • velocity -- int16

This callback is triggered when the threshold as set by set_velocity_callback_threshold is reached. The response value is the velocity value of the sensor.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by set_debounce_period.